Fix id conversion issue in delayed_sidekiq strategy

[sundus-y]

Ensure ids extracted from Redis remain strings, preventing UUID issues. Previously, ids were being converted to integers, causing problems with UUIDs in the delayed_sidekiq strategy.

This update also enhances the test suite:

• Existing tests are updated.
• A new test ensures the issue is resolved.

Due to SQLite's lack of UUID support, a stub_uuid_model method is added. This method stubs models with UUIDs, using SecureRandom.uuid for the primary key.

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Before submitting the PR make sure the following are checked:

• [x] The PR relates to only one subject with a clear title and description in grammatically correct, complete sentences.
• [x] Wrote good commit messages.
• [x] Commit message starts with [Fix #issue-number] (if the related issue exists).
• [x] Feature branch is up-to-date with master (if not - rebase it).
• [x] Squashed related commits together.
• [x] Added tests.
• [x] Added an entry to the changelog if the new code introduces user-observable changes. See changelog entry format for details.